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US7087025B2 - Blood pressure determination based on delay times between points on a heartbeat pulse - Google Patents

Blood pressure determination based on delay times between points on a heartbeat pulse Download PDF

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Publication number
US7087025B2
US7087025B2 US10/502,932 US50293204A US7087025B2 US 7087025 B2 US7087025 B2 US 7087025B2 US 50293204 A US50293204 A US 50293204A US 7087025 B2 US7087025 B2 US 7087025B2
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pulse
blood pressure
heartbeat
time
delay times
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US10/502,932
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US20050096551A1 (en
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Martin C. Baruch
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Empirical Technologies Corp
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Empirical Technologies Corp
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Assigned to EMPIRICAL TECHNOLOGIES CORPORATION reassignment EMPIRICAL TECHNOLOGIES CORPORATION ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: BARUCH, MARTIN C.
Publication of US7087025B2 publication Critical patent/US7087025B2/en
Priority to US11/500,558 priority patent/US8100835B2/en
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Assigned to NAVY, SECRETARY OF THE, UNITED STATES OF AMERICA reassignment NAVY, SECRETARY OF THE, UNITED STATES OF AMERICA CONFIRMATORY LICENSE (SEE DOCUMENT FOR DETAILS). Assignors: EMPIRICAL TECHNOLOGIES CORPORATION
Assigned to SUNTECH MEDICAL, INC. reassignment SUNTECH MEDICAL, INC. SECURITY AGREEMENT Assignors: EMPIRICAL TECHNOLOGIES CORPORATION
Priority to US13/231,703 priority patent/US20120238887A1/en
Assigned to CARETAKER MEDICAL, LLC reassignment CARETAKER MEDICAL, LLC LICENSE (SEE DOCUMENT FOR DETAILS). Assignors: EMPIRICAL TECHNOLOGIES CORPORATION
Assigned to EMPIRICAL TECHNOLOGIES CORPORATION reassignment EMPIRICAL TECHNOLOGIES CORPORATION TERMINATION OF DEVELOPEMENT & LICENSE AGREEMENT & AMENDMENT THERETO Assignors: SUNTECH MEDICAL INC
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    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/02—Detecting, measuring or recording for evaluating the cardiovascular system, e.g. pulse, heart rate, blood pressure or blood flow
    • A61B5/021—Measuring pressure in heart or blood vessels
    • A61B5/02108—Measuring pressure in heart or blood vessels from analysis of pulse wave characteristics
    • A61B5/02125—Measuring pressure in heart or blood vessels from analysis of pulse wave characteristics of pulse wave propagation time
    • A—HUMAN NECESSITIES
    • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
    • A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
    • A61B5/00—Measuring for diagnostic purposes; Identification of persons
    • A61B5/72—Signal processing specially adapted for physiological signals or for diagnostic purposes
    • A61B5/7235—Details of waveform analysis
    • A61B5/7253—Details of waveform analysis characterised by using transforms
    • A61B5/7257—Details of waveform analysis characterised by using transforms using Fourier transforms

Definitions

  • This invention is concerned with the measurement of blood pressure (BP), and more particularly with non-occlusive, passive blood pressure measurements, using a sensor of heartbeat pulses at a single site, and with a resolution sufficient to resolve Pulsus Paradoxus (PP).
  • BP blood pressure
  • PP Pulsus Paradoxus
  • Two-site measurement approaches have been especially deficient in the measurement of systolic variations, because the heartbeat pressure pulse changes in shape and amplitude as it heads toward the arterial periphery. These changes are due to a number of factors, including changes in the arterial wall material composition that affect the wall's elastic behavior, the taper of the main arterial branch, the distribution of branch lines, and pulse reflections. The result is that the pulse steepens and contracts as it propagates, as linear pulse propagation models predict. Additionally, non-linear effects in the arterial tree can produce pulse steepening. More importantly, the non-linear elastic response of the arterial wall results in a distinctly non-linear relationship of pulse propagation velocity and pressure.
  • An object of the present invention is to avoid problems and disadvantages of multiple-site blood pressure measurements and to provide single-site measurement of blood pressure with less complexity and lower cost than has heretofore been possible.
  • the present invention avoids the problems due to different pressure-induced pulse-shape modulations associated with different pulse detection sites, by detection of single heartbeat pulses at a single site and by analysis of individual pulses.
  • the present invention makes use of the fact that changes in time delay between different parts of a heartbeat pulse, subjected to different arterial pressures, reflect changes in blood pressure.
  • FIG. 1 is a block diagram of an apparatus for implementing the invention
  • FIG. 2 shows a heartbeat pulse and certain percentages of the full amplitude (pulse peak);
  • FIGS. 3A and 3B are a single-pulse BP determination flow chart
  • FIG. 4 shows a raw data stream
  • FIG. 5 shows a filtered data stream
  • FIG. 6 shows zero-crossing detection
  • FIG. 7 shows slope values obtained for points about each zero-crossing
  • FIG. 8 shows an onset slope of a heartbeat pulse
  • FIG. 9 shows interbeat interval and systolic delay-time-derived BP evolution
  • FIG. 10 is another single-pulse BP determination flow chart
  • FIG. 11 shows a heartbeat pulse with back-end time delay analysis
  • FIG. 12 shows evolution of delay time for back-end analysis
  • FIG. 13 shows interbeat interval and delay time evolution for back-end analysis
  • FIG. 14 shows an overlay of systolic BP evolutions measured using the invention and a Colin Pilot BP monitor
  • FIG. 15 shows evolution of averaged delay time for a series of percentiles
  • FIG. 16 shows derived delay pressure as well as interbeat interval
  • FIG. 17 shows filtered Pulsus Paradoxus component for measurements using the invention and also the Colin Pilot.
  • FIG. 1 illustrates an apparatus for implementing the invention, including a sensor 10 linked to a computer 12 (or other appropriate device) having a display 14 .
  • the sensor detects heartbeat pulses at a single site (such as the wrist) on a body through which blood flows.
  • Analysis performed by the computer determines delay times between predetermined points on each heartbeat pulse, and the delay times are used by the computer to obtain a measurement of blood pressure.
  • Various outputs from the computer (later described) can be viewed on the display and recorded.
  • systolic blood pressure is determined by measuring delay times between a reference point on the onset slope of the heartbeat pulse, located, for example, at 50% of the full amplitude (peak) of the heartbeat pulse, and points on the onset slope that are located at predetermined percentages of the pulse peak.
  • FIG. 2 shows the profile of a heartbeat pulse and shows percentage points on the onset slope between the pulse onset and the pulse peak.
  • the present invention may use any appropriate sensor for detecting heartbeat pulses at a single site.
  • the sensor may be of the fiber-optic type disclosed in U.S. Pat. No. 6,463,187 granted Oct. 8, 2002, which responds to radial artery displacements at the wrist.
  • a completely integrated wireless sensor unit is employed featuring a fiber-optic sensor, 16-bit analog digital conversion at 512 Hz, amplification, a digital transmission system operating at 916.5 Mhz with a raw data rate of 250 Kbps using Manchester encoding, as well as an on-board Microchip PIC16C67 (OTP Version) operating at 20 MHz.
  • This unit communicates with a PC computer via an antenna that is plugged into a serial port. It is apparent that the invention is not limited to such a sensor unit.
  • FIGS. 3A and 3B show a single-pulse BP determination flow chart in accordance with an embodiment of the invention. This embodiment is merely an example of the manner in which the invention can be implemented and is not intended to limit the invention.
  • a heartbeat pulse data stream is acquired for a given period of time, such as four to eight seconds, from a sensor (step 1 ). See FIG. 4 .
  • the acquired data stream is filtered by a fast Fourier transform filter, removing DC offsets and centering the data stream about zero (step 2 ). See FIG. 5 .
  • Peak/pulse detection of the filtered data is performed, in which the zero crossing of the onset slope of each heartbeat pulse is detected (step 3 ). See FIGS. 6 and 7 .
  • the onset slope of each heartbeat pulse is then fitted using a ninth order polynomial (step 4 ). See FIG. 8 . While other functional forms can be used, the functional form of an arterial pulse propagation model would be preferred.
  • the fitted function is used to determine the pulse onset and peak, and the time positions of a sequence of percentages of the full pulse amplitude (step 5 ). See FIG. 2 .
  • Steps 6 and 7 illustrate in detail the manner in which step 5 is performed.
  • an effective delay time is then calculated (step 8 ) and is used to determine blood pressure (step 9 ). See FIG. 9 .
  • the equation in step 9 has two parameters that are adjusted to fit the data, one being the exponential decay constant ⁇ , and the other a constant pressure offset C.
  • a distance has to be invoked, as indicated in the pressure expression.
  • the distance taken to be 1 meter, is not part of the fitting parameters, but simply a constant. Due to the nature of the logarithmic function, adjusting the distance accomplishes the same as adjusting the constant C; it provides a constant offset for the pressure.
  • the scaling of the delay time to pressure is influenced solely by the choice of the exponential parameter.
  • FIG. 9 conveys a sense of the degree to which Pulsus Paradoxus (PP) can be resolved with the single-point delay-time method of the invention.
  • FIG. 9 presents the PP modulations, converted into units of pressure from the measured delay times, as well as the interbeat interval, derived from the same data stream.
  • delay times are obtained between points on the onset slope (front-end) of the heartbeat pulse, and more particularly, systolic blood pressure is determined from such delay times.
  • FIG. 10 is a single-pulse BP determination flowchart for measurement of both systolic and diastolic blood pressure by calculation of delay times in both systolic and diastolic regimes on the back-end of the heartbeat pulse.
  • the acquisition of a data stream, the filtering of data, and the max/min determination can be performed as in the first embodiment.
  • time positions of predetermined points on the back end of the pulse are established (step 10 ). See FIG. 11 .
  • Data points between predetermined percentiles on the back side of the heartbeat pulse are linearly fitted, and based on these fits, a revised time determination of a predetermined number (e.g., 4) of percentiles is computed (Step 11 ).
  • the delay time pressure obtained in accordance with the invention is the result of converting a sequence of delay time measurements between 55% and 85% of the full height of a given pulse on the falling side (back-end) of the pulse. These measurements were obtained at the wrist of a subject.
  • a data acquisition rate of 512 Hz, corresponding to a resolution of about 2 milliseconds, is sufficient to resolve delay time changes that are on the order of tens of milliseconds on the front-end (onset slope) of a heartbeat pulse and more by a factor of 4 to 5 on the back-end.
  • the spectral content of the heartbeat pulse in the arterial periphery extends maximally to about 30 Hz, with the significant amplitude-carrying harmonics being in the range of up to 15–20.
  • the heartbeat pressure is therefore bandwidth-limited, that is, except for noise interference, no spectral surprises lurk in higher frequency bands that could produce aliasing.
  • FIG. 15 shows evolution of averaged delay time for a series of percentiles on the pulse onset slope.
  • the delay time pressure gives a peak-to-peak Pulsus of 6.37 mmHg with an error of 0.44 mmHg.
  • FIG. 13 An interesting observation from FIG. 13 is that the artery's non-linear time-pressure relationship can be discerned. Visual comparison of the delay time modulations, presumably due to Pulsus during the first 30 seconds and the modulations during the 40–100 second period, reveals a significant difference in amplitude. This difference is essentially eliminated as the result of the non-linear conversion seen in FIG. 14 .
  • both BP traces presented in FIG. 16 were Fourier filtered between 0.1 and 0.4 Hz.
  • the results are presented in FIG. 17 .
  • the peak-to-peak mean of all the positive and negative peak amplitudes was determined.
  • the average PP is 5.28 mmHg, with an error of 0.34 mmHg.
  • the corresponding values are 4.61 mmHg, with an error of 0.5 mmHg.
  • Appendices I and II showing examples of a single-point delay-time algorithm and single-point delay-time functions for implementing the invention pursuant to the above-described embodiments. It is apparent that other algorithms and functions can be used to implement the invention.

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  • Health & Medical Sciences (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Cardiology (AREA)
  • Engineering & Computer Science (AREA)
  • Heart & Thoracic Surgery (AREA)
  • Physiology (AREA)
  • Biophysics (AREA)
  • Pathology (AREA)
  • Vascular Medicine (AREA)
  • Biomedical Technology (AREA)
  • Physics & Mathematics (AREA)
  • Medical Informatics (AREA)
  • Molecular Biology (AREA)
  • Surgery (AREA)
  • Animal Behavior & Ethology (AREA)
  • General Health & Medical Sciences (AREA)
  • Public Health (AREA)
  • Veterinary Medicine (AREA)
  • Measuring Pulse, Heart Rate, Blood Pressure Or Blood Flow (AREA)
US10/502,932 2001-02-26 2003-01-29 Blood pressure determination based on delay times between points on a heartbeat pulse Expired - Lifetime US7087025B2 (en)

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Application Number Priority Date Filing Date Title
US10/502,932 US7087025B2 (en) 2002-01-29 2003-01-29 Blood pressure determination based on delay times between points on a heartbeat pulse
US11/500,558 US8100835B2 (en) 2004-07-29 2006-08-08 Arterial pulse decomposition analysis for vital signs determination
US13/231,703 US20120238887A1 (en) 2001-02-26 2011-09-13 Hydrostatic finger cuff for blood wave form analysis and diagnostic support

Applications Claiming Priority (6)

Application Number Priority Date Filing Date Title
US35221302P 2002-01-29 2002-01-29
US37139902P 2002-04-11 2002-04-11
US38743502P 2002-06-11 2002-06-11
US41034902P 2002-09-13 2002-09-13
PCT/US2003/002490 WO2003063687A2 (fr) 2002-01-29 2003-01-29 Determination de la pression sanguine sur la base d'un temps d'attente entre des points d'une impulsion cardiaque
US10/502,932 US7087025B2 (en) 2002-01-29 2003-01-29 Blood pressure determination based on delay times between points on a heartbeat pulse

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US09/763,657 Continuation-In-Part US6723054B1 (en) 1998-08-24 1999-08-24 Apparatus and method for measuring pulse transit time

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US11/500,558 Continuation-In-Part US8100835B2 (en) 2001-02-26 2006-08-08 Arterial pulse decomposition analysis for vital signs determination

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US20100139418A1 (en) * 2006-03-28 2010-06-10 University Of Southern California Measurement of sliding friction-induced vibrations for biomimetic tactile sensing
US7986990B2 (en) 2009-04-01 2011-07-26 John Dinwiddie System and method for detecting extremely low frequency electric fields in the human body
WO2012015426A1 (fr) 2010-07-30 2012-02-02 Empirical Technologies Corporation Appareil de support de diagnostic
US8216136B2 (en) 2009-03-05 2012-07-10 Nellcor Puritan Bennett Llc Systems and methods for monitoring heart rate and blood pressure correlation
US8290730B2 (en) 2009-06-30 2012-10-16 Nellcor Puritan Bennett Ireland Systems and methods for assessing measurements in physiological monitoring devices
US8398556B2 (en) 2008-06-30 2013-03-19 Covidien Lp Systems and methods for non-invasive continuous blood pressure determination
US8463347B2 (en) 2009-09-30 2013-06-11 Nellcor Puritan Bennett Ireland Systems and methods for normalizing a plethysmograph signal for improved feature analysis
US8506498B2 (en) 2008-07-15 2013-08-13 Nellcor Puritan Bennett Ireland Systems and methods using induced perturbation to determine physiological parameters
US8532751B2 (en) 2008-09-30 2013-09-10 Covidien Lp Laser self-mixing sensors for biological sensing
US8560245B2 (en) 2003-07-07 2013-10-15 Nellcor Puritan Bennett Ireland Continuous non-invasive blood pressure measurement apparatus and methods providing automatic recalibration
US8628477B2 (en) 2009-07-31 2014-01-14 Nellcor Puritan Bennett Ireland Systems and methods for non-invasive determination of blood pressure
US8660799B2 (en) 2008-06-30 2014-02-25 Nellcor Puritan Bennett Ireland Processing and detecting baseline changes in signals
US8825428B2 (en) 2010-11-30 2014-09-02 Neilcor Puritan Bennett Ireland Methods and systems for recalibrating a blood pressure monitor with memory
US8898037B2 (en) 2010-04-28 2014-11-25 Nellcor Puritan Bennett Ireland Systems and methods for signal monitoring using Lissajous figures
US9060695B2 (en) 2011-11-30 2015-06-23 Covidien Lp Systems and methods for determining differential pulse transit time from the phase difference of two analog plethysmographs
US9066660B2 (en) 2009-09-29 2015-06-30 Nellcor Puritan Bennett Ireland Systems and methods for high-pass filtering a photoplethysmograph signal
US9198582B2 (en) 2009-06-30 2015-12-01 Nellcor Puritan Bennett Ireland Determining a characteristic physiological parameter
US9220440B2 (en) 2009-09-21 2015-12-29 Nellcor Puritan Bennett Ireland Determining a characteristic respiration rate
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